End-capped polymer chains and products thereof

ABSTRACT

According to an aspect of the present invention, a method is provided in which a double diphenylethylene compound is reacted with a polymer that contains a carbocationically terminated chain thereby providing a 1,1-diphenylene end-functionalized chain. Subsequently, an alkylating agent is reacted with the 1,1-diphenylene end-functionalized chain, thereby providing an alkylated 1,1-diphenylene end-functionalized chain. In some embodiments, the method further comprises (a) optionally combining a 1,1-diphenylorganolithium compound with the alkylated 1,1-diphenylene end-functionalized polymer followed by (b) reacting an organolithium compound with the alkylated 1,1-diphenylene end-functionalized polymer. This provides an anionically terminated polymer, which can be used, for example, in subsequent anionic polymerization and coupling reactions. According to another aspect of the present invention, a novel polymer is provided that comprises a polymer chain, which chain further comprises the following: (a) a plurality of constitutional units that correspond to cationically polymerizable monomer species and (b) an end-cap comprising a  
                 
 
group or a  
                 
 
group, where R is a branched or unbranched alkyl group containing from 1 to 20 carbons and R 1  is a branched, unbranched, or cyclic alkyl group or an aryl group, containing from 1 to 20 carbons. Other aspects of the present invention relate to novel copolymers that comprise: (a) a first polymer block that comprises a plurality of constitutional units that correspond to isobutylene; and (b) a second polymer block that comprises a plurality of constitutional units that correspond to hydroxyethyl methacrylate.

FIELD OF THE INVENTION

This invention relates to processes for end-capping a cationicallypolymerized polymer. More particularly this invention relates toprocesses for end-capping a cationically polymerized polymer with ananionic group, after which the resulting anionically terminated polymercan be used in subsequent anionic reactions, including anionic couplingand polymerization reactions.

BACKGROUND OF THE INVENTION

It is well known that living polymerization (i.e., polymerizationproceeding in the practical absence of chain transfer and termination)is a very useful method for designing polymer structures, permitting forexample, control of the molecular weight and molecular weightdistribution of the polymer, as well as enabling functional groups to bepositioned at desired points in the polymer chain. Since Szwarc et al.demonstrated the living nature of polystyryllithium formed from thereaction of sodium naphthalene and styrene in the 1950s, a wide varietyof living polymerization schemes have been developed, includingcationic, anionic, radical, ring-opening, and group transferpolymerization.

Copolymers are an important class of polymers and have numerouscommercial applications. For instance, their unique properties, whetherin pure form, in blends, in melts, in solutions, and so forth, lead totheir use in a wide range of products, for example, compatiblilizers,adhesives and dispersants. An advantage of combining variouspolymerization techniques (e.g., cationic and anionic polymerizationtechniques in the case of the present invention) is that new copolymers,each with its own unique properties, can be prepared which could nototherwise be prepared using a single polymerization method.

For example, polyisoolefins are attractive materials because the polymerchain is fully saturated and, consequently, the thermal and oxidativestability of this polymer are excellent. Polyisoolefins are prepared bycationic polymerization. Recently, Muller et al. reported thatpoly(alkyl methacrylate)-b-polyisobutylene and poly(alkylmethacrylate)-b-polyisobutylene-b-poly(alkyl methacrylate) copolymerscan be prepared by the combination of cationic and anionicpolymerization techniques. See Feldthusen, J.; Iván, B.; Müller, A. H.E. Macromolecules, 1997, 30, 6989-6993; Feldthusen, J.; Iván, B.;Müller, A. H. E. Macromolecules 1998, 31, 578-585. In this process, anend-functionalized polyisobutylene (PIB), specifically1,1-diphenyl-1-methoxy end-functionalized polyisobutylene,

or 2,2-diphenylvinyl end-functionalized polyisobutylene,

is prepared by the reaction of living polyisobutylene with1,1-diphenylethylene. The chain end of the resulting polymer issubsequently metallated with alkali metal compounds such assodium/potassium alloy or cesium in tetrahydrofuran at room temperature.The thus produced macroanion is capable of polymerizing monomer. Thismethod, however, is inconvenient because of the complicated process forthe metallation of the polymer chain using alkali metal compounds.

A more recent attempt to combine cationic and anionic polymerizationtechniques involves the preparation of end-functionalized polymers(e.g., end-functionalized polyisobutylene) by reacting acarbocationically terminated polymer with a heterocyclic compound (e.g.,thiophene) to provide an end-capped polymer (e.g., thiopheneend-functionalized polyisobutylene). The end-capped polymer is thenreacted with an organolithium compound to yield an anionicallyterminated polymer, which is subsequently reacted with an anionicallypolymerizable monomer such as tert-butyl methacrylate to produce acopolymer. See, Application Ser. No. 60/480,121 filed Jun. 20, 2003 andentitled “End-Capped Polymer Chains and Products Thereof”, andMartinez-Castro, N,; Lanzendo1fer, M. G.; Muller, A. H. E.; Cho, J. C.;Acar, M. H.; and Faust, R. Macromolecules 2003, 36, 6985-6994. Anadvantage of this process is that simple and complete metallation isachieved. This process, however, is also subject to improvement. Forexample, in the case where thiophene end-functionalized polyisobutyleneis formed, to prevent coupling between thiophene functionalizedpolyisobutylene and living polyisobutylene, an excess of thiophene isused while functionalizing the polyisobutylene cation with thethiophene. Moreover, the blocking efficiency was found to be only about80% even when a low molecular weight product is targeted.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a method is providedin which a double diphenylethylene compound is reacted with a polymerthat contains a carbocationically terminated chain, which chain containsa plurality of constitutional units corresponding to cationicallypolymerizable monomer species, thereby providing a 1,1-diphenyleneend-functionalized chain. Subsequently, an alkylating agent is reactedwith the 1,1-diphenylene end-functionalized chain, resulting in theformation of an alkylated 1,1-diphenylene end-functionalized chain.

In certain embodiments, the above method further comprises (a)optionally combining a 1,1-diphenylorganolithium compound with thealkylated 1,1-diphenylene end-functionalized polymer to removeimpurites, followed by (b) reacting an organolithium compound with thealkylated 1,1-diphenylene end-functionalized polymer, resulting in theformation of an anionically terminated polymer, which can be used, forexample, in subsequent anionic polymerization and coupling reactions.

According to another aspect of the present invention, a novel polymer isprovided that comprises a polymer chain, which chain further comprisesthe following: (a) a plurality of constitutional units that correspondto cationically polymerizable monomer species and (b) an end-capcomprising a diphenylethylene group. Examples of diphenylethylene groupsinclude

groups and

groups, where R is a branched or unbranched alkyl group, typicallycontaining from 1 to 20 carbons, more typically containing from 1 to 10carbons. In other aspects, the end-cap comprises a

group or a

group, where R is a branched or unbranched alkyl group containing from 1to 20 carbons and R₁ is a branched, unbranched, or cyclic alkyl group oran aryl group, containing from 1 to 20 carbons

According to yet another aspect of the present invention, a novelcopolymer is provided, which includes: (a) a first polymer block thatcomprises a plurality of constitutional units corresponding tocationically polymerizable monomer species, (b) a second polymer blockthat comprises a plurality of constitutional units corresponding toanionically polymerizable monomer species, and (c) a linking moietywhich links the first and second polymer blocks together selected from a

group and a

group (for example, a linking moiety selected from a

group and a

group), where R is a branched or unbranched alkyl group, typicallycontaining from 1 to 20 carbons, more typically containing from 1 to 10carbons, and where R₁ is a branched, unbranched, or cyclic alkyl groupor an aryl group, also typically containing from 1 to 20 carbons, moretypically containing from 1 to 10 carbons.

Other aspects of the present invention relate to novel copolymers thatcomprise: (a) a first polymer block that comprises a plurality ofconstitutional units that correspond to isobutylene; and (b) a secondpolymer block that comprises a plurality of constitutional units thatcorrespond to hydroxyethyl methacrylate. Examples include copolymers inwhich (a) the first block is a polyisobutylene block and (b) the secondpolymer block is a poly(hydroxyethyl methacrylate) block or is a randompolymer block that contains constitutional units corresponding tohydroxyethyl methacrylate and to methyl methacrylate.

An advantage of the present invention is that copolymers can be preparedvia the combination of living cationic polymerization and living anionicpolymerization. Hence, copolymers containing one or more cationicallypolymerized blocks and one or more anionically polymerized blocks can beformed.

Another advantage of the present invention is that end-capped polymersformed of cationically polymerizable monomers can be quantitativelyreacted with organolithium compounds to form stable anionicmacroinitiators, which are then available for numerous anionicpolymerization and coupling reactions.

These and other aspects, embodiments and advantages of the presentinvention will be more fully understood upon review of the DetailedDescription to follow.

DETAILED DESCRIPTION

As is well known, polymers are molecules that contain one or morechains, each containing multiple copies of one or more constitutionalunits. An example of a common polymer is polystyrene

where n is an integer, typically an integer of 10 or more, moretypically on the order of 10's, 100's, 1000's or even more, in which theconstitutional units in the chain correspond to styrene monomers:

(i.e., they originate from, or have the appearance of originating from,the polymerization of styrene monomers—in this case the additionpolymerization of styrene monomers). Copolymers are polymers thatcontain at least two dissimilar constitutional units. As used herein apolymer “block” is defined as a grouping of 10 or more constitutionalunits, commonly 20 or more, 50 or more, 100 or more, 200 or more, 500 ormore, or even 1000 or more units, and can be branched or unbranched. A“chain” is a linear (unbranched) grouping of 10 or more constitutionalunits (i.e., a linear block). In the present invention, theconstitutional units within the blocks and chains are not necessarilyidentical, but are related to one another by the fact that that they areformed in a common polymerization technique, e.g., a cationicpolymerization technique or anionic polymerization technique.

In accordance with one aspect of the present invention, copolymers areprovided which include (a) one or more blocks which contain a pluralityof constitutional units that correspond to one or more cationicallypolymerizable monomer species and (b) one or more blocks which contain aplurality of constitutional units that correspond to one or moreanionically polymerizable monomer species. These constitutional unitsoccur within the copolymer molecule at a frequency of at least 10 times,and more typically at least 50, 100, 500, 1000 or more times.

The copolymers of the present invention embrace a variety ofconfigurations, including linear and branched configurations. Branchedconfigurations include star-shaped configurations (e.g., configurationsin which three or more chains emanate from a single region), combconfigurations (e.g., graft copolymers having a main chain and aplurality of side chains), and dendritic configurations (e.g.,arborescent or hyperbranched copolymers).

Some examples of cationically polymerizable monomer species follow: (a)olefins, including isomonoolefins with 4 to 18 carbon atoms per moleculeand multiolefins with 4 to 14 carbon atoms per molecule, for example,isobutylene, 2-methylbutene, isoprene, 3-methyl-1-butene,4-methyl-1-pentene, beta-pinene, and the like, (b) vinyl aromatics suchas styrene, alpha-methyl styrene, para-chlorostyrene,para-methylstyrene, and the like, and (c) vinyl ethers such as methylvinyl ether, isobutyl vinyl ether, butyl vinyl ether, N-vinyl carbazole,and the like.

Examples of anionically polymerizable monomer species include thefollowing: acrylates, methacrylates, styrene, styrene derivatives, andconjugated dienes including 1,3-butadiene and isoprene. Of particularbenefit are acrylate or methacrylate monomers having the formulaCH₂═CHCO₂R or CH₂═C(CH₃)CO₂R where R is a substituted or unsubstituted,branched, unbranched or cyclic alkyl groups containing 1 to 20 carbons.Substituents for the alky groups include hydroxyl, amino and thiolfunctional groups, among others. In embodiments where monomers areutilized that have functional groups, proper protection of thefunctional group is commonly needed during the course of anionicpolymerization. Specifc examples of nonfunctional and protectedfunctional methacrylate monomers include ethyl methacrylate, methylmethacrylate, tert-butyl methacrylate, isodecyl methacrylate, dodecylmethacrylate, stearyl methacrylate, glycidyl methacrylate,2-[(trimethylsilyl)oxy]ethyl methacrylate,2-[(tert-butyldimethylsilyl)oxy]ethyl methacrylate, and2-[(methoxymethyl)oxy]ethyl methacrylate.

The copolymers of the present invention tyically have a molecular weightranging from 200 to 2,000,000, more typically from 500 to 500,000. Theratio of constitutional units corresponding to the cationicallypolymerized monomers (e.g., isobutylene) relative to the constitutionalunits corresponding to the anionically polymerized monomers (e.g.,methyl methacrylate) in the copolymer usually ranges from 1/99 to 99/1w/w, preferably from 30/70 to 95/5 w/w. In some embodiments, copolymersare provided which have a narrow molecular weight distribution such thatthe ratio of weight average molecular weight to number average molecularweight (Mw/Mn) (i.e., the polydispersity index) of the polymers rangesfrom about 1 to 10, or even from about 1 to 2.

As a specific example, block copolymers of the formula X(PCA-C-PAN)_(n)are formed in various embodiments of the invention, where X correspondsto the initiator species, C corresponds to the capping species, PCA is apolymer block comprising a plurality of constitutional units thatcorrespond to one or more anionically polymerizable monomer species, forexample, a polyolefin block, PAN is a is polymer block comprising aplurality of constitutional units that correspond to one or moreanionically polymerizable monomer species, for example, a poly(methylmethacrylate) block, and n is a positive whole number. Linear blockcopolymers are formed where n=1 or n=2. Where n=2, the copolymers aresometimes referred to as triblock copolymers. This terminologydisregards the presence of the initiator fragment, for example, treatingPCA-X-PCA as a single olefin block, with the triblock therefore denotedas PCA-PAN-PCA. Star shaped copolymers are formed where n=3 or more. Thevalue of n is typically dictated by the functionality of the initiatormolecule, with monofunctional initiators corresponding to n=1,difunctional initiators corresponding to n=2, and so forth.

In accordance with another aspect of the present invention, copolymersare made by a process that includes: (a) providing a 1,1-diphenyleneend-functionalized polymer (which polymer contians one or morecationically polymerizable monomer species); and (b) reacting the1,1-diphenylene end-functionalized polymer with an organometalliccompound to yield an anionically terminated polymer (also referred toherein as a “macrocarbanion”, or a “anionic macroinitiator” based on itsability to initiate further reactions such as coupling andpolymerization reactions.

For instance, in accordance with an embodiment of the present inveniton,a living macrocarbocation, e.g., living cationic polyisobutylene, isreacted with a double diphenylethylene, e.g.,1,3-bis(1-phenylethenyl)benzene (sometimes referred to as meta-doublediphenylethylene) or 1,4-bis(1-phenylethenyl)benzene (sometimes referredto as para-double diphenylethylene), to produce a 1,1-diphenylethyleneend-functionalized carbocationic polymer. The carbocation is thenalkylated with a suitable alkylating agent, e.g., with an organometalliccompound such as dimethylzinc, whereupon the resulting macromonomer isreadily metallated with a suitable organometallic compound such as analkyllithium compound, thereby providing a living anionic macroinitiatorin near quantitative yield. A sterically hindered lithium compound,e.g., a 1,1-diphenylalkyllithium species, is used in certain embodimentsto remove impurities that may be present alongside the1,1-diphenylethylene end-functionalized polymer, thereby preventingpremature termination of the living macroanion.

In some embodiments, anionic macroinitiators formed in accordance withthe present invention are used to synthesize star polymers (e.g.,polyisobutylene stars), for example, by reacting the macroinitiatorswith coupling molecules such as unhindered chlorosilanes. Chlorosilaneshave been used previously to couple living anionic chain ends to formstar polymers in Roovers, J. E. L. and S. Bywater, Macromolecules 1972,5, 385 and in Application Ser. No. 60/480,121 filed Jun. 20, 2003.

In some embodiments, anionic macroinitiators formed in accordance withthe present invention are used to efficiently initiate livingpolymerization of ionically polymerizable monomer species, e.g.,acrylate or methacrylate monomers, yielding block copolymers with highblocking efficiency. The “blocking or crossover efficiency” is thepercentage of macroanions that actually initiate polymerization (ofacrylate or methacrylate monomers in this instance). The resulting blockcopolymers, e.g., diblock polymers, triblock copolymers, radial-shapedblock copolymers, etc., will exhibit properties that depend upon thecationically and anionically polymerizable species found within theblock copolymer, as well as their absolute and relative amounts.

In other embodiments of the invention, block copolymers are reacted(subsequent to anionic polymerization and before anion quenching) withcoupling molecules such as (di- or trichloromethyl)benzene or (di- ortribromomethyl)benzene, thereby forming larger-scale copolymers (e.g.,PIB-PMMA stars) Application Ser. No. 60/480,121 filed Jun. 20, 2003.

Further details are provided below.

Preparation of 1,1-Diphenylethylene End-Functionalized Polymers.

In accordance with an embodiment of the present invention,1,1-diphenylethylene end-functionalized polymers are prepared from aliving carbocationic polymer. Carbocationically terminated polymers arecommonly formed at low temperature from a reaction mixture thatcomprises: (a) an initiator, (b) a Lewis acid coinitiator, (c) acationically polymerizable monomer, (c) an optional proton scavenger and(d) an optional diluent.

Suitable initiators include organic ethers, organic esters, and organichalides. Initiators may be monofunctional, difunctional, trifunctionaland so forth, thereby producing, for example, diblock copolymers,triblock copolymers, and radial-shaped block copolymers, respectively.Specific examples include tert-alkyl chloride, cumyl ethers, cumylhalides, cumyl esters, and hindered versions of the same, for instance,2-chloro-2,4,4-trimethylpentane,5-tert-butyl-1,3-bis(1-chloro-1-methylethyl)benzene,5-tert-butyl-1,3-bis(1-methoxy-1-methylethyl)benzene,5-tert-butyl-1,3-bis(1-acetoxy-1-methylethyl)benzene,1,3,5-tris(1-chloro-1-methylethyl)benzene,1,3,5-tris(1-methoxy-1-methylethyl)benzene, and1,3,5-tris(1-acetoxy-1-methylethyl)benzene.

Examples of suitable Lewis acid coinitiators include metal halides andalkyl metal halides such as boron trichloride, titanium tetrachlorideand alkyl aluminum halides (e.g., chlorodiethyl aluminum, dichloroethylaluminum, chlorodimethyl aluminum, dichloromethyl aluminum). A commonlyused coinitiator is titanium tetrachloride. The coinitiator is usuallyused in concentrations equal to or greater than that of initiator, e.g.,1 to 100 times higher, preferably 2 to 40 times higher than that ofinitiator.

A proton scavenger, typically a Lewis base, typically provided to ensurethe virtual absence of protic impurities, such as water, which can leadto polymeric contaminants in the final product. Examples of protonscavengers (also referred to as proton traps) include stericallyhindered pyridines, for example, substituted or unsubstituted2,6-di-tert-butylpyridines, such as 2,6-di-tert-butylpyridine and4-methyl-2,6-di-tert-butylpyridine, as well as1,8-bis(dimethylamino)-naphthalene and diisopropylethyl amine. Theproton trap is usually used at the concentration of 1 to 10 times higherthan that of protic impurities in the polymerization system.

The varoius reactions of the present invention are tyically carried outin the presence of a diluent or a mixture of diluents. For the thecationic polymerization and end-capping reactions, typical diluentsinclude (a) halogenated hydrocarbons which contain from 1 to 4 carbonatoms per molecule, such as methyl chloride and methylene dichloride,(b) aliphatic hydrocarbons and cycloaliphatic hydrocarbons which containfrom 5 to 8 carbon atoms per molecule, such pentane, hexane, heptane,cyclohexane and methyl cyclohexane, or (c) mixtures thereof. Forexample, in some embodiments, the solvent system contains a mixture of apolar solvent, such as methyl chloride, methylene chloride and the like,and a nonpolar solvent, such as hexane, cyclohexane or methylcyclohexaneand the like.

Regardless of the synthesis technique, once a desired livingcarbocationically terminated polymer is obtained, it is then availablefor 1,1-diphenylethylene end-funcitonalization using a doublediphenylethylene species, for example, 1,3-bis(1-phenylethenyl)benzene,

or 1,4-bis(1-phenylethenyl)benzene,

The 1,4-bis(1-phenylethenyl)benzene is tyically more beneficial than the1,3-bis(1-phenylethenyl)benzene for the functionalization of both livinganionic and cationic polymers, because a coupled product is tyically notgenerated where the 1,4-bis(1-phenylethenyl)benzene is employed. In thepresent invention, double diphenylethylene is tyically employed at aconcentration that is 1 to 10 times higher than that of the initiator,more typically 1 to 6 times higher than that of the initiator. In thisregard, it is known that 1,1-diphenylethylene end-functionalizedpolyisobutylene can be prepared by the reaction of a living cationicpolymer such as polyisobutylene with 1,3-bis(1-phenylethenyl)benzene or1,4-bis(1-phenylethenyl)benzene. See Bae, Y. C.; Faust, R.Macromolecules 1998, 31(26), 9379-9383. Unfortunately, the quenchingreaction of a living diphenyl carbenium ion (e.g., a polymerend-functionalized with 1,1-Diphenylethylene carbocation) with methanolintroduces a labile methoxy group at the chain end, which will lead toside reactions. Side reactions include the termination of subsequentlyadded organolithium compounds as well as the macroinitiators that areformed from the subsequently added organolithium coupounds.

To prevent this, in various embodiments of the present invention, the1,1-diphenylethylene carbocation is subjected to an alkylation reaction.In general, the alkylation is carried out with an organometalliccompound, such as an alkyl aluminum compound and an alkyl zinc compoundwhich typically contains from 1 to 20 carbon atoms, for example,selected from various branched or unbranched alkyl groups. In thepresent invention, the alkyl aluminum or alkyl zinc compound istypically used at a concentration ranging from 0.1 to 100 times thecoinitiator concentration, more typically 0.1 to 10 times thecoinitiator concentration.

-   -   Bae, Y. C.; Kim, I-J.; Faust, R. Polymer Bulletin 2000, 44(5-6),        453-459, has reported the methylation of    -    with dimethylzinc to form

Temperatures for the polymerization of the cationically polymerizablemonomer, as well as the subsequent end-functionalization and alkylationof the resulting living polymer, will typically range from 0° C. to−150° C., more tyipcally from −10° C. to −90° C. Reaction time for thecationic polymerization and the functionalization and alkylation of ofthe resulting living cationic polymer will typically range from a fewminutes to 24 hours, more typically from 10 minutes to 10 hours.

The number average molecular weight of the resulting1,1-diphenylethylene end-functionalized polymer will typically rangefrom 1,000 to 1,000,000, more typically from 5,000 to 500,000.

A specific example of a procedure for the preparation of1,1-diphenylethylene end-functionalized polymers follows. First, aliving caibocationically terminated polymer, e.g., carbocationicallyterminated polyisobutylene, is obtained by adding a coinitiator into apolymerization zone (e.g., a flask), which contains initiator, protontrap, monomer and diluent as discussed above. After polymerizatoin ofthe monomer is complete, the resulting living cationic polymer, in thisinstance, living carbocationically terminated polyisobutylene (PIB),

is reacted with a double diphenylethylene species, in this example1,4-bis(1-phenylethenyl)benzene,

for example, by dissolving the double diphenylethylene species in adiluent and charging it to the polymerization zone, whereupon acarbenium cation, e.g.,

is formed. An alkyl zinc or alkyl aluminum compound, e.g., dimethylzinc(CH₃)₂Zn, is then supplied to alkylate the carbenium ion, for example,by dissolving it in a diluent and charging the resulting solution to thepolymerization zone. Prechilled alcohol is then charged to thepolymerization zone to quench the reaction. The resulting1,1-diphenylethylene end-functionalized polymer product, e.g.,

is then recovered.Preparation of Block Copolymer Using 1,1-DiphenylethyleneEnd-Functionalized Macromer.

Once a 1,1-diphenylethylene end-functionalized macromer is provided, itis readily metallated with an organometallic compound, and the resultinganionic macroinitiator is then available for a variety of reactions,including the living anionic polymerization reactions and anioniccoupling reactions.

Organometallic compounds suitable for the metallation of the1,1-diphenylethylene end-functionalized macromer can be selected, forexample, from a wide range of organolithium compounds of the formula RLiin which R is a hydrocarbon group, typically containing from 1 to 20carbon atoms per molecule, for example, selected from unbranched alkylgroups, branched alkyl groups, cyclic alkyl groups, mono-ring arylgroups and multi-ring aryl groups. Specific examples of suitableorganolithium compounds include methyllithium, ethyllithium,isopropyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium,tert-octyllithium, phenyllithium, 1-naphthyllithium, p-tolyllithium,cyclohexyllithium, and 4-cyclohexylbutyllithium. Organolithium compoundsare typically used at concentrations that are 1 to 50 times the1,1-diphenylethylene end-functionalized macromer concentration, moretypically 1 to 10 times the macromonomer concentration.

The metallation, as well as subsequent living anionic polymerization andcoupling processes, are typically carried out in the presence of adiluent or mixture of diluents. Suitable diluents include hydrocarbonsolvents, for example, paraffinic, cycloparaffinic, and aromatichydrocarbon solvents, and polar solvents, for example, ethers such astetrahydrofuran, dimethylether, diethylether, dioxane, and1,2-dimethoxyethane.

Reaction times between the organolithium compound and the1,1-diphenylethylene end-functional polymer will typically range from afew minutes to 24 hours, more typically from 1 hour to 12 hours.Temperatures for the reaction between the organolithium compound and the1,1-diphenylethylene end-functional polymer will typically range from30° C. to −100° C., more typically from 30° C. to −90° C.

In some embodiments, a small amount of a sterically hindered lithiumcompound is charged to the polymerization zone prior to introducing thealkyllithium compound to remove impurities that are frequently present,thereby preventing termination during the reaction of the alkyllithiumcompound with the 1,1-diphenyethylene end-functionalized polymer.Because the 1,1-diphenylalkyllithium cannot react with1,1-diphenylethylene end-functionalized polymer due to steric effects,its addition is effective for purposes of removing impurities that arepresent in the solution.

Examples of sterically hindered organolithium compounds includeorganolithium compounds of the formula RC(Ø₁)(Ø₂)Li in which R is ahydrocarbon group, typically containing 1 to 20 carbon atoms permolecule, including unbranched alkyl groups, branched alkyl groups,cyclic alkyl groups, mono-ring aryl groups, and multi-ring aryl groups,and Ø₁ and Ø₂ can be the same or different and are selected fromunsubstituted or substituted, mono- or multi-ring, aryl groups.Commonly, the sterically hindered organolithium compound is a1,1-diphenylalkyllithium compound.

1,1-Diphenylalkyllithium may be generated, for example, from thereaction of an alkyllithium compound and 1,1-diphenylethylene at roomtemperature in the presence of diluent. 1,1-Diphenylethylene istypically used in concentrations equal to or less than that of thealkyllithium in this reaction. A example of one beneficial1,1-diphenylalkyllithium compound is 1 1,1-diphenylhexyllithium,

The sterically hindered organolithium compound is typically added to asolution containing the 1,1-diphenylethylene end-functional polymer anda diluent or mixture of diluents, for example, at room temperature.Afterwards, the organolithium compound is added to the1,1-diphenylethylene functional polymer, for instance, under anionicreaction conditions (e.g., at −78° C.). After a stable livingmacroinitiator is formed in this fashion, any unreacted alkyllithium maybe destroyed by heating, for example, to 40° C. in the presence of areactive species such as tetrahydrofuran (which can also be used as adiluent).

The resulting anionic macroinitiator is then available for subsequentpolymerization or coupling reactions, as desired. For example, in someembodiments, an anionically reactive species such as an anionicallypolymerizable monomer are added under polymerization conditions (e.g.,at −78° C.) to the macroinitiator. After the desired reaction iscompleted, purified alcohol is typically charged to the polymerizationzone to quench the reaction.

Times for anionic polymerization will typically range from a few minutesto 24 hours, more typically from 5 minutes to 12 hours. Temperatures foranionic polymerization will typically range from 0° C. to −100° C., moretypically from −10° C. to −90° C.

As a specific example, the reaction of a 1,1-diphenylethyleneend-functionalized macromer, for example, 1,1-diphenylethyleneend-functionalized polyisobutylene (see above), with an organolithiumcompound, for example, n-butyl lithium, results in the formation of acarbanion, e.g.,

Subsequent exposure of the carbanion to an anionically polymerizablemonomer, e.g., a methacrylate monomer such as methyl methacrylate (MMA),results in a copolymer having (a) a cationically polymerized block, forexample, a polyisobutylene block, and (b) an anionically polymerizedblock, for example, a poly(methyl methacrylate) (PMMA) block:

EXAMPLES

Characterizations. ¹H-NMR spectroscopy was carried out on a Bruker AC250 MHz spectrometer at 25° C. in CDCl₃. Gel Permeation Chromatorgraphy(GPC) was carried out using a Waters HPLC system equipped with model 510HPLC pump, model 410 differential refractometer, model 486 UV/visibledetector, model 712 sample processor, and five ultra-Styragel columnsconnected in the series (500, 10³, 10⁴, 10⁵ and 100 Å). THF was used asan eluent at a flow rate of 1 mL/min.

Materials. 2,6-Di-tert-butylpyridine (Aldrich, 97%) was purified bydistillation from CaH₂. Isobutylene (Air Gas) was passed through in-linegas purifier columns packed with CaSO₄ and no. 13 molecular sieves andcondensed at −15° C. prior to polymerization. Methyl chloride (CH₃Cl)was passed through in-line gas purifier columns packed with BaO/Drieriteand condensed at −80° C. prior to polymerization. Methylene chloride(CH₂Cl₂) was purified by washing it with 10% aqueous NaOH and then withdistilled water until neutral and dried over anhydrous MgSO₄ overnight.It was refluxed for 24 h and distilled from CaH₂, just before use.n-Hexane was rendered olefin free by refluxing it over concentratedsulfuric acid for 48 h. It was washed with 10% aqueous NaOH and thenwith deionized water until neutral and stored over MgSO₄ for 24 h. Itwas refluxed over CaH₂ overnight and distilled. Titanium (IV) chloride(TiCl₄, Aldrich, 99.9%) was used as received.2-Chloro-2,4,4-trimethylpentane was prepared by hydrochlorination of2,4,4-trimethyl-1-pentene (Fluka, 98%) with hydrogen chloride gas in drydichloromethane at 0° C. Kaszas, G.; Gyor, M.; Kennedy, J. P.; Tüdös, F.J. Macromol. Sci., Chem 1983, A18, 1367-1382. The product was dried overCaCl₂ and distilled under reduced pressure before use.5-tert-butyl-1,3-bis(1-chloro-1-methylethyl)benzene was synthesizedfollowing the procedure reported in Gyor, M. Wang., H. C.; Faust, R. J.J. Macromol. Sci., Pure Appl. Chem 1992, A29, 639. Tetrahydrofuran(Merck p.a) was purified first by distillation under nitrogen from CaH₂and then by refluxing over potassium. n-Butyllithium (n-BuLi, 2.5 M inhexane) was purchased from Aldrich and its concentration was titrated bya standard method. See, e.g., Reed, P. J.; Urwin, J. R. J. Organometal.Chem. 1972, 39, 1-10. Methyl methacrylate (MMA) and2-[(trimethylsilyl)oxy]ethyl methacrylate (TMSiOEMA), in which thehydroxyl group of 2-hydroxyethyl methacrylate (HEMA) is protected with atrimethylsilyl group, were dried over CaH₂ for 24 h and then distilledover triethylaluminum or trioctylaluminum under vacuum. The1,4-Bis(1-phenylethenyl)benzene is synthesized using procedures likethat described in U.S. Pat. No. 4,182,818 to Tung, L. H. and Lo, G.Y.-S. 1,1-Diphenylethylene purchased from Aldrich Chemical Company waspurified by vacuum distillatin under potassium metal.

Synthesis of 1,1-diphenyhexyllithium. The preparation of1,1-diphenylhexyllithium is carried out under high vacuum conditions(<10⁻⁶ mbar). 0.037 g of n-butyllithium (5.7×10⁻⁴ mol) is added at −78°C. to a reactor containing 0.01 mL of 1,1-diphenylethylene (5.7×10⁻⁵mol) dissolved in tetrahydrofuran. After 5 minutes, the cherry-reddishsolution is brought to room temperature for 1 hour. During this step,unreacted n-butyllithium is decomposed by the reaction withtetrahydrofuran. The solution is delivered into a graduated cylinderwith a stopcock, which is stored in a refrigerator.

Synthesis of α,ω-1,1-diphenylethylene end-functionalizedpolyisobutylene. The preparation of a difunctional macromonomer iscarried out at −80° C. under nitrogen atmosphere. To a prechilled 500 mL3-neck flask equipped with mechanical stirrer are added sequentially 187mL of hexane, 111 mL of methyl chloride, 0.086 g of5-tert-butyl-1,3-bis(1-chloro-1-methylethyl)benzene (3.0×10⁻⁴ mol), 0.2mL of 2,6-di-tert-butylpyridine (9.0×10⁻⁴ mol), and 21 mL of isobutylene(0.27 mol). Then, 1.2 mL of titanium tetrachloride (1.1×10⁻² mol) isadded into the reactor to polymerize the isobutylene. After thecompletion of monomer polymerization, 0.34 g of1,4-bis(1-phenylethenyl)benzene (1.2×10⁻³ mol) dissolved in methylenechloride is added into the reactor. After 2 hours, 5.15 g ofdimethylzinc (5.4×10⁻² mol) dissolved in toluene is added into thereactor. 2 hours later, 30 mL of prechilled methanol is added into thereactor to quench the reaction. The polymer solution is then poured intoammonium hydroxide/methanol (10/90, v/v). After the evaporation ofsolvents, the polymer is dissolved in hexane and inorganics arefiltered. The polymer recovered by the precipitation of the polymersolution into methanol. The polymer is then dissolved again in hexaneand recovered again by the precipitation of the polymer solution intomethanol, followed by drying in a vacuum.

According to ¹H NMR and GPC measurements, functionalization andmethylation at polyisobutylene chain ends are essentially complete.Essentially no change in the number average molecular weight andpolydispersity of the 1,1-diphenylethylene functional polyisobutylenewas observed, relative to those of the polyisobutylene precursor (Table1), confirming that coupling reactions are virtually nonexistant. TABLE1 Polymer M_(n) M_(w)/M_(n) Polyisobutylene 55000 1.03α,ω-1,1-Diphenylethylene 56800 1.04 end-functional polyisobutylene

Synthesis of 1,1-diphenylethylene end-functionalized polyisobutylene.The preparation of monofunctional macromonomer is carried out at −80° C.under nitrogen atmosphere. To a prechilled 500 mL flask equipped withmechanical stirrer are added sequentially 198 mL of hexane, 118 mL ofmethyl chloride, 0.1 mL of 2-chloro-2,4,4-trimethylpentane (6.0×10⁻⁴mol), 0.2 mL of 2,6-di-tert-butylpyridine (9.0×10⁻⁴ mol), and 4.7 mL ofisobutylene (0.06 mol). 1.2 mL of titanium tetrachloride (1.1×10⁻² mol)is then added into the reactor to polymerize the isobutylene. After thecompletion of monomer polymerization, 0.34 g of1,4-bis(1-phenylethenyl)benzene (1.2×10⁻³ mol) dissolved in methylenechloride is added into the reactor. After 2 hours, 5.15 g ofdimethylzinc (5.4×10⁻² mol) is added into the reactor. After 2 morehours, 30 mL of prechilled methanol is added into the reactor to quenchthe reaction. The polymer solution is then poured into ammoniumhydroxide/methanol (10/90, v/v). After the evaporation of solvents, thepolymer is dissolved in hexane and inorganics are filtered. The polymersolution is then precipitated into methanol to give solid polymer. Thesolid polymer is again dissolved in hexane and recovered again by theprecipitation of the polymer solution into methanol, followed by dryingunder vacuum.

According to ¹H NMR and GPC measurements, functionalization andmethylation at the polyisobutylene chain end are essentially complete.Number average molecular weight and polydispersity of1,1-diphenylethylene functional polyisobutylene did not changesubstantiallly as compared with those of polyisobutylene (Table 2),confirming a virtual absence of coupling reactions. TABLE 2 PolymerM_(n) M_(w)/M_(n) Polyisobutylene 4500 1.09 ω-1,1-Diphenylethylene end-4900 1.08 functional polyisobutylene

Example 1

All chemical purifications and acrylate polymerizations are carried outunder high vacuum condition (<10⁻⁶ mbar). 1.17 g (2.06×10⁻⁵ mol) ofα,ω-1,1-diphenylethylene end-functionalized polyisobutylene(M_(n)=56800, see above) in 250 mL of hexane is stirred over calciumhydride for 24 hours. The polymer solution is then filtered to removecalcium hydride. The hexane solvent is evaporated, and 100 mL oftetrahydrofuran are added to the remaining polymer. This polymersolution is then added to a reactor equipped with a stirrer.1,1-diphenylhexyllithium in tetrahydrofuran (see above) is added intothe reactor dropwise until the color of the polymer solution changesfrom colorless to yellowish. The amount of 1,1-diphenylhexyllithium usedfor this purpose is 0.0010 g (4.1×10⁻⁶ mol). The polymer solution issubsequently cooled down to −78° C. with vigorous stirring. After 10minutes at this temperature, 0.0090 g of n-butyllithium (1.4×10⁻⁴ mol)in 27.5 mL of hexane is added into the reactor. 12 hours later, thepolymer solution is heated up to 40° C. and kept at this temperature for1 hour. The polymer solution is again cooled to −78° C. After 10 minutesat this temperature, 0.95 mL of methyl methacrylate (8.9×10⁻³ mol) isdistilled into the reactor. The reactoin is quenched after 5 hours byadding purified degassed methanol to the reactor. The polymer solutionis precipiated into methanol to give a white solid polymer.

The blocking efficiency of the obtained block copolymer is measuredusing GPC and ¹H NMR and is calculated to be at leaset 87%. The productis immersed into hexane for 24 hours to isolate polyisobutylenehomopolymer from the block copolymer. According to ¹H NMR and GPCmeasurements, the purified block copolymer has a M_(n)=109400, aM_(w)/M_(n)=1.14, and the composition of isobutylene and methylmethacrylate in the polymer is 57/43 w/w.

Example 2

1.60 g (2.8×10⁻⁵ mol) of α,ω-1,1-diphenylethylene end-functionalizedpolyisobutylene (M_(n)=56800, see above) in 200 mL of hexane is stirredover calcium hydride for 24 hours. The polymer solution is then filteredto remove calcium hydride. Solvent is evaporated, and 100 mL oftetrahydrofuran is added to the remaining polymer. The polymer solutionis then added to a reactor equipped with a stirrer, and1,1-diphenylhexyllithium in tetrahydrofuran (see above) is added intoreactor dropwise until the color of the polymer solution changes fromcolorless to yellowish. The amount of 1,1-diphenylhexyllithium used forthis purpose is 0.0010 g (4.1×10⁻⁶ mol). The polymer solution issubsequently cooled to −78° C. with vigorous stirring. After 10 minutesat this temperature, 0.0122 g of n-butyllithium (1.9×10⁻⁴ mol) in 40 mLof hexane is added into the reactor. After an additional 12 hours, thepolymer solution is heated to 40° C. and kept at this temperature for 1hour. The polymer solution is then cooled down to −78° C. After 10minutes at this temperature, 0.64 mL of methyl methacrylate (6.0×10⁻³mol) is distilled into the reactor. 5 hours later, purified methanol isadded to reactor to quench the reaction. The polymer solution is pouredinto methanol to yield a white solid polymer.

The blocking efficiency of the obtained block copolymer is measuredusing GPC and ¹H NMR and is calculated to be at least 92%. The blockcopolymer is purified by using hexane to remove polyisobutylenehomopolymer. According to ¹H NMR and GPC measurements, the purifiedblock copolymer had a M_(n)=83400, a M_(w)/M_(n)=1.30, and thecomposition of isobutylene and methyl methacrylate in the polymer is67/33 w/w.

Example 3

1.96 g (3.45×10⁻⁵ mol) of α,ω-1,1-diphenylethylene end-functionalizedpolyisobutylene (M_(n)=56800, see above) in 300 mL of hexane is stirredover calcium hydride for 24 hours. The polymer solution is then filteredto remove calcium hydride. The solvent is evaporated and 130 mL oftetrahydrofuran are added to the remining polymer. The resulting polymersolution is then added to a reactor equipped with a stirrer.1,1-diphenylhexyllithium in tetrahydrofuran (see above) is then addedinto reactor dropwise until the color of the polymer solution changesfrom colorless to yellowish. The amount of 1,1-diphenylhexyllithium usedfor this purpose is 0.0030 g (1.2×10⁻⁵ mol). Afterwards, the polymersolution is cooled down to −78° C. with vigorous stirring. After 10minutes at this temperature, 0.0160 g of n-butyllithium (2.5×10⁻⁴ mol)in 40 mL of hexane is added into the reactor. 2 hours later, the polymersolution is heated to 40° C. and kept at this temperature for 1 hour.Then, the polymer solution is again cooled to −78° C. After 10 minutesat this temperature, 2 mL of 2-[(trimethylsilyl)oxy]ethyl methacrylate(9.2×10⁻³ mol) diluted with 2 mL of tetrahydrofuran is added into thereactor. 3 hours later, purified methanol is added to reactor to quenchthe reaction. The polymer solution is precipitated into methanol toyield a white solid polymer.

The blocking efficiency is at least 90%, as measured using GPC and ¹HNMR. The obtained polymer is purified by using hexane to removepolyisobutylene homopolymer. During the recovery step, thetrimethylsilyloxy groups in the block copolymer are completely convertedinto hydroxyl groups. For ¹H NMR and GPC measurements, the blockcopolymer is treated with benzoic anhydride to protect the hydroxylgroups in the poly(2-hydroxylethyl methacrylate) blocks with a benzoylgroup. According to ¹H NMR and GPC measurements, the block copolymertreated with benzoic anhydride had a M_(n)=131900, a M_(w)/M_(n)=1.33,and the composition of isobutylene and 2-hydroxylethyl methacrylate inthe polymer is 50/50 w/w.

Example 4

0.93 g (1.9×10⁻⁴ mol) of ω-1,1-diphenylethylene end-functionalizedpolyisobutylene (M_(n)=4900, see above) in 200 mL of hexane is stirredover calcium hydride for 24 hours. Then, the polymer solution isfiltered to remove calcium hydride. Solvent is evaporated, and 100 mL oftetrahydrofuran is added to the remaining polymer. The polymer solutionis added to a reactor equipped with a stirrer. Unlike the aboveexamples, no 1,1-diphenylhexyllithium in tetrahydrofuran is then addedto the reactor at this point. The polymer solution is cooled down to−78° C. with vigorous stirring. After 10 minutes at this temperature,0.0961 g of n-butyllithium (1.5×10⁻³ mol) is added into the reactor. 1hour later, the polymer solution is heated to 20° C. and kept at thistemperature for 1 hour. Then, the polymer solution is again cooled to−78° C. After 10 minutes at this temperature, 1.5 mL of methylmethacrylate (1.4×10⁻² mol) is charged into the reactor. 2 hours later,purified methanol is added to reactor to quench the reaction. Thepolymer solution is then poured into methanol to yield a white solidpolymer.

The blocking efficiency is calculated to be 67% based on GPC and ¹H NMRresults. The obtained polymer is purified using hexane to removepolyisobutylene homopolymer. According to ¹H NMR and GPC measurements,the purified block copolymer has a M_(n)=22300, a M_(w)/M_(n)=1.26, andthe composition of isobutylene and methyl methacrylate in the polymer is25/75 w/w.

Example 5

0.24 g of >1,1-diphenylethylene end-functionalized polyisobutylene(M_(n)=4900, see above) in 200 mL of hexane is stirred over calciumhydride for 24 hours. Then, the polymer solution is filtered to removecalcium hydride. Solvent is evaporated and 100 mL of tetrahydrofuran isthen added to the remaining polymer. The polymer solution is added to areactor equipped with a stirrer. No 1,1-diphenylhexyllithium intetrahydrofuran is added to the reactor at this point. The polymersolution is then cooled down to −78° C. with vigorous stirring. After 10minutes, 0.0275 g of n-butyllithium (4.3×10⁻⁴ mol) is added into thereactor. 1 hour later, the polymer solution is heated up to 20° C. andkept at this temperature for 1 hour. The polymer solution is then cooleddown to −78° C. After 10 minutes at this temperature, 0.6 mL of methylmethacrylate (5.6×10⁻³ mol) is distilled into the reactor. 2 hourslater, purified methanol is added to reactor to quench the reaction. Thepolymer solution is then poured into methanol to yield a white solidpolymer.

The blocking efficiency is calculated to be 72% based on GPC and ¹H NMRresults. The obtained polymer is purified using hexane to removepolyisobutylene homopolymer. According to ¹H NMR and GPC measurements,the purified block copolymer had a M_(n)=31700, a M_(w)/M_(n)=1.13, andthe composition of isobutylene and methyl methacrylate in the polymer is18/82 w/w.

Example 6

0.14 g of 1,1-diphenylethylene end-functionalized polyisobutylene(M_(n)=4900, see above) in 200 mL of hexane is stirred over calciumhydride for at least 24 hours. The polymer solution is then filtered toremove calcium hydride. Solvent is evaporated and 100 mL oftetrahydrofuran is added to polymer. The polymer solution is added to areactor equipped with a stirrer. No 1,1-diphenylhexyllithium intetrahydrofuran is added to the reactor at this point. The polymersolution is then cooled down to −78° C. with vigorous stirring. After 10minutes at this temperature, 0.016 g of n-butyllithium (2.5×10⁻⁴ mol) isadded into the reactor. 1 hour later, the polymer solution is heated upto 20° C. and kept for 1 hour at this temperature. The polymer solutionis again cooled down to −78° C. After 10 minutes at this temperature,0.4 mL of methyl methacrylate (3.7×10⁻³ mol) is charged into thereactor. 2 hours later, purified methanol is added to reactor to quenchthe reaction. The polymer solution is then poured into methanol to yielda white solid polymer.

The blocking efficiency is calculated to be 68%, based on GPC and ¹H NMRresults. The obtained polymer is purified by using hexane to removepolyisobutylene homopolymer. According to ¹H NMR and GPC measurements,the purified block copolymer has a M_(n)=36900, an M_(w)/M_(n)=1.20, andthe composition of isobutylene and methyl methacrylate in the polymer is15/85 w/w.

Although various embodiments are specifically illustrated and describedherein, it will be appreciated that modifications and variations of thepresent invention are covered by the above teachings and are within thepurview of the appended claims without departing from the spirit andintended scope of the invention.

1. A polymer comprising a polymer chain that comprises (a) a pluralityof constitutional units that correspond to cationically polymerizablemonomer species and (b) an end-cap comprising a

group or a

group, where R is a branched or unbranched alkyl group containing from 1to 20 carbons and R₁ is a branched, unbranched, or cyclic alkyl group oran aryl group, containing from 1 to 20 carbons.
 2. The polymer of claim1, wherein R₁ is n-pentyl or 2-methyl-butyl.
 3. The polymer of claim 2,wherein R is methyl or ethyl.
 4. The polymer of claim 1, wherein thenumber average molecular weight of said polymer ranges from 5,000 to500,000.
 5. The polymer of claim 1, wherein said chain comprises aplurality of constitutional units that correspond to two or morediffering cationically polymerizable monomer species.
 6. The polymer ofclaim 1, wherein said polymer comprises two or more of said polymerchains
 7. The polymer of claim 1, wherein said constitutional unitscorrespond to isobutylene. 8-34. (canceled)